I think it's kind of a wasteful philosophy to assume that everyone should have their own independent piece of land. If both parties are content to stay under the same roof, what's the problem?
I do think that we should think about other ways to compel maturity, though. For at least the last twenty years, college has been a means of extending adolescence. We need to address the problems there that teach kids to fear love and commitment (a symptom of the high divorce rate and perverted concepts on the family).
The marriage age needs to come back down to ~21-25, kids in college shouldn't be given a pass to party or live recklessly. People do what's expected of them.